1. Field of the Invention
This invention relates to a separator/feeder for sheets of paper or paper-like medium for taking out such a medium. More particularly, the present invention relates to a separator/feeder for sheets of paper or paper-like medium that separates and feeds sheets of such a medium one by one from a pile of sheets of the medium.
2. Description of the Related Art
An apparatus adapted to check and process sheets of paper or paper-like medium (to be simply referred to as paper-like medium hereinafter) such as a printer, a copying machine, an automatic teller machine, a banknote processing machine, a mail matter processing machine or the like handles sheets of paper-like medium such as sheets of printing paper, banknotes, sheets of copying paper, sealed letters, postcards, cards securities or the like, whichever appropriate. More specifically, such an apparatus is required to take out sheets one by one from a pile of a plurality of sheets of paper-like medium. Therefore, such a checking apparatus is equipped with a separator/feeder for separating and feeding sheets of paper-like medium one by one from a pile of sheets of paper-like medium. For example, a banknote processing section of an automatic teller machine repeats an operation of taking out a banknote from a pile of banknotes stored in an input/output section or a depository and examines it. Thus, an automatic teller machine is equipped with a separator/feeder for separating banknotes one by one from a pile of banknotes.
Conventionally, separators/feeders for separating and feeding sheets of paper-like medium from a pile of sheets of paper-like medium are required to accurately feed sheets one by one without duplication as the most important requirement that have to meet. Sheets of paper-like medium are apt to be adsorbed by each other in a pile because some of the sheets are inevitably frayed at the time of manufacturing, if slightly, and loosened fibers become entangled or the sheets are held in tight contact with each other or generate static electricity. To date, such sheets of paper-like medium are mostly separated by applying a strong force to the uppermost surface of the piled sheets and a predetermined number of sheets of paper-like medium are stripped off from the pile. Then, the sheets that are stripped off are separated from each other by a duplicate feeding prevention mechanism or the like and fed into the host apparatus one by one. Various techniques are selectively employed in such duplicate feeding prevention mechanisms and the sheets that are laid one on the other and taken out from the pile as a bunch are forced into a narrow gap and separated from each other by the most popular one of the known techniques. For example JP-A 2003-261238 (KOKAI) discloses a technique with which rollers are arranged at the opposite sides of a narrow gap to rotate in various different directions and sheets that are laid one on the other are forced to pass through the gap. Then, the sheets are subjected to forces in opposite directions and separated from each other. However, in many occasions, it is difficult to reliably and satisfactorily separate sheets into individual ones by means of such a mechanism. In other words, sheets of paper-like medium that are strongly adhering to each other can be caught by the gap and locked there to give rise to a trouble of bringing the apparatus to a halt.
Techniques of applying vibrations to the uppermost surface of a pile of sheets of paper-like medium to separate the sheets with ease have been discussed. For example, JP-A 2004-2044 (KOKAI) discloses a technique of applying vibrations to sheets of paper-like medium. With this technique, a beam-shaped vibrating part is applied to the entire surface of a pile of sheets of paper-like medium in the transversal direction at a position located immediately upstream relative to a feed mechanism to reduce the adhesion of the sheets so as to operate as an auxiliary means of a duplicate feeding prevention mechanism. For this purpose, a bar-shaped vibrating part having a length greater than the width of the sheets of paper-like medium is arranged upstream relative to a takeout roller and sheets of paper-like medium are fed while it is being vibrated.
However, the arrangement of applying vibrations to sheets of paper-like medium when taking out the sheets of paper-like medium as disclosed in JP-A 2004-2044 (KOKAI) is accompanied by a problem as described below. As a result of an experiment conducted by the inventors of the present invention, it is indispensably necessary to apply appropriate pressure between the vibrator and the sheets of paper-like medium in order to vibrate the piled sheets of paper-like medium and loosen them. In other words, the effect of separating sheets of paper-like medium is not obtained simply by controlling the height of the uppermost sheet as described in JP-A 2004-2044 (KOKAI).
A mechanism for separating sheets of paper-like medium by applying vibrations to the sheets of paper-like medium until they start vibrating as disclosed in JP-A 2002-356240 (KOKAI). However, the disclosed mechanism can be used only in an apparatus where a paper-like medium having certain predetermined characteristics is supplied and additionally it is not possible to separate sheets of paper-like medium by means of the mechanism unless pressure of an appropriate pressure level is applied to the vibrator. The mechanism disclosed in FIG. 3 of JP-A 2000-177869 (KOKAI) cannot separate sheets of paper-like medium for a similar reason.
Additionally, the paper-like medium feeding position of conventional paper-like medium processing machine is fixed and the machine is so devised that a take out mechanism such as a takeout roller operates to take out sheets of paper-like medium while applying appropriate pressure to the sheets. More specifically, JP-A 2000-219334 (KOKAI) discloses a mechanism comprising a movable lever that is held in contact with the top surface of piled sheets of paper-like medium to detect the position of the top surface and constantly keep the top surface of the piled sheets of paper-like medium to a same position. In short, it is possible for the prior art to take out sheet of paper-like medium reliably without depending on the type of paper-like medium only by means of such a mechanism.
However, the mechanism of using a vibrator held in contact with the surface of piled sheets of paper-like medium is accompanied by a problem that the pressure being applied by the vibrator resists the operation of taking sheets of paper-like medium one by one. Particularly, when sheets of paper-like medium is soft, the sheets of paper-like medium are pressed down by and engaged with the vibrator to adversely affect the operation of taking them out. Therefore, it may be necessary to regulate the pressure according to the state of being pressed down.
As pointed out above, mechanisms for preventing duplicate feeding that takes place when sheets of paper-like medium tightly adhere to each other by means of ultrasonic vibrations are accompanied by a problem that the technique of controlling the pressure applied to piled sheets of paper-like medium by means of a vibrator is not reliably established.